Seals to seal flanges, especially ring packings to seal flange connections on two pipes being connected, for example, gas pipes or the like, are already known.
The relevant prior art is explained, for example, with reference to FIG. 9. This essentially depicts a flange connection 70 for pipes in which two pipe elements being joined end to end, namely a first pipe element 71 and a second pipe element 72, are to be sealed together. The first pipe element 71 has a corresponding first pipe flange 75 with a first outer periphery 77 and the second pipe element 72 has a corresponding second pipe flange 76 with a second outer periphery 78. A ring packing 84, for example, made of a fibrous material, is situated in the region between the pipe flanges 75 and 76 facing each other end to end. The first pipe flange 75 and the second pipe flange 76 of flange connection 70 are held in a pressed together position by means of an arrangement in which this arrangement consists essentially of a first pressure disk 79 connected to the first pipe flange 75 and a second pressure disk 80 connected accordingly to the second pipe flange 76. The first pressure disk 79 and second pressure disk 80 are joined by means of a clamping bolt 81, which passes through corresponding holes of the first pressure disk 79 and the second pressure disk 80 and is fastened by means of a first nut 82 connected to the first pressure disk 79 and a second nut 83 connected to the second pressure disk 80. Centering of ring packing 84 is essential for proper function of the ring packing 84 in the region of flange connection 70, in which according to the prior art explained with reference to FIG. 9 this centering occurs by means of a clamping bolt 81. To accomplish this the ring packing 84 is provided on the outside periphery with a centering edge 85 that comes in contact with clamping bolt 81. To achieve this type of centering, however, the ring packing 84 is displaced radially in the region of the pipe flanges 75 and 76 facing each other so that, on the one hand, a first dead space 86 is produced in the region of an opening 89 of ring packing 84 opposite a cylindrical inside periphery 73 of the first pipe element and a cylindrical inside periphery 74 of the second pipe element 72, whereas, on the other hand, a projection 87 of the ring packing 84 corresponding to the first dead space 86 is present in the region of the cylindrical inside periphery 73 or the cylindrical inside periphery 74. Owing to this centering, as shown in FIG. 9, a second dead space 88 is also produced on the opposite peripheral region 77, 78 of flange connection 70, i.e., the ring packing 84 is displaced inward in the radial direction by a certain distance opposite the first pipe flange 75 and the second pipe flange 76. However, in the flange connection according to the prior art apparent from FIG. 9 precise centering of the ring packing 84 is not possible owing to the relatively high tolerances. Because of the dead spaces occurring in such an arrangement, for example, dead spaces 86 and 88, as well as the protrusion 87 of ring packing 84, an adverse effect and narrowing in the inside diameter of flange connector 70 occurs. Another shortcoming results from the dead spaces produced by rebound of ring packing 84 between the first pipe flange 75 and the second pipe flange 76, i.e., the first dead space 86 and the second dead space 88.
Ring packings for flange connections for pipes are also known that consist of turned parts, i.e., parts that are turned from the solid material, in which a corresponding centering edge is turned on the ring packing. The drawback of such known seals consists of the fact that the choice of material for this purpose is limited and they are extremely costly to manufacture. For example, so-called collar seals are known that are turned from sintered polytetrafluoroethylene.
Seals consisting of molded materials to seal flat surfaces are also known in which the materials employed for this purpose exhibit greater thicknesses and as a result lead to sealing drawbacks, especially high cold flow and poor chemical resistance.
Finally, seals produced from several individual parts are known, for example, ring packings to seal a flange connection of two glass tubes according to DE-U 92 05 669.5. These known seals consist, in particular, of a thin plastic film, for example, a film of stretched, microporous polytetrafluoroethylene, in which this film is tightened in a mounting or attachment ring and glued or sealed to this ring or mechanically attached to this ring. The shortcomings of such seals composed of several individual parts consist of the high manufacturing costs, the relatively wide centering edge and, in the case of a glued joint with the outer mounting or attachment ring, relatively poor chemical resistance of the resulting ring packing.
Relative to the prior art just outlined the underlying task of the present invention is to provide an improved process for manufacturing a seal using a compactable sealing material, especially a fluoropolymer, to seal flanges, preferably matching flanges (for example, flat or spherical), especially a process for manufacturing a ring packing to seal flange connections for pipes, in which this seal is provided on the outer and/or inner periphery with a corresponding centering collar.